Extensometer or strain gauge



NM". 2,1948- F. c. MOSTERTZ 2,4525860 EXTENSOMETE IR OR STRAIN GAUGE Filed June 12, 1947 2 Sheets-Sheet l Nov. 2 1948. F. c. MOSTERTZ 2,452,860

v EXTENSOMETER OR STRAIN GAUGE 2 Sheets-Sheet 2 Filed June 12, 1947 INVENTOR.

and in the claims.

- tion of the principles involved.

" Figure 8 is a perspective ofv the spring;

Patented Nov. '2, i 1948 j'l JNITED STATES PATENT OFFICE EXTENSOMETER R STRAIN GAUGE Franz C(Mostertz, Philadelphia, Pa., assignor to F. F. Met'zger and Son, Philadelphia, Pa., a

Application June 12, 1947, Serial No. 754,177

Claims. (01. 33-148) My invention relates to extensometer orstrain gauges of themechanical type.

A purpose of my invention is to simplifythe fabrication of the bearing gauge pin and lever assembly of a mechanical extensometer.

V A further purpose is to avoid difificulty, -in;replacement of broken parts at the bearing.

A further purpose is to place knife edges; on the cheek plates of an extensometer; to place knife edge slots in a desirable circular bearing shaft supported on the knife edges, to mount the bearing shaft intermediate its knife edge slots in a transverse hole of a bearing block, and

to surround the bearing block by a lever extension mounted on the bearing block and preferably having openings passing the ends of the on the opposite end of the lever block from thegauge pin, preferably in a slot extending across :the-lever block and the bearing shaft.

-- Further purposes appear in the specification In the drawings I have chosen to illustrate only one of the numerous embodiments in whichmy invention may appear, choosing the form shown from the standpoints of convenience in -illustration, satisfactory operation and clear demonstra- Figure 1 is a partially broken front elevation of an extensometer embodying the present invention.

Figure 2 is a fragmentary enlargement of Figure 1. Figure 3 is a left end elevation of Figure 2.

Figure 4 is a section of Figure 2 on the line 4-4.

Figure 5 is a section of Figure 3 on the line 's-5. I Figure 6 is a fragmentary perspective of the lever block, lever extension and beari haft. Figure 7 is a detailed perspective of ,the lever block and bearing shaft from which theilejver extension has been removed.

Figure 9 is afragmentary perspective bearing assembly.

In the drawings like numerals refer to like of the .parts. Describing in illustration but not in limitation, and referring to the drawings. I

The present invention relates to extensometer or strain gauges of the character employed to 21 and 28.

2 measure strain in tensile testing, and also in testing of machines, vehicles, building, bridges and other civil and mechanical engineering structures.

The present invention is a development of Metzger U. S. Patent No. 1,884,073, granted 00- tober 25, 1932, for extensometer and is designed to overcome difiiculties which have been developed in the construction of the device there shown.

In the Metzger device, a triangular bearing shaft is employed, which is notched to permit the passage of the lever spring and which rides against the retainer. The engaged pin is supported directly on the end of the lever. fabrication of this character of bearing is quite expensive due to the necessity of machining and inserting the triangular bearing shaft. Due to the notch, the bearing shafts are subject to rather frequent breakage, and replacement is troublesome and expensive in this method of fabrication.

In accordance with the present invention the lever is made up primarily of a lever extension which may be conveniently a stamping, and the gauge pin and bearing shaft are both supported and united to the lever extension by a lever block which is readily removable from the lever extension. The lever block is comparatively simple from a machining standpoint and the bearing men or suitable structural elements having gauge marks 2! and 22. The gauge mark 2| receives the end of a movable gauge pin 23 supported on the extensometer lever to be described, while the gauge mark 22 receives a stationary gauge pin 24 at, a suitable spaced difference along the extensometer. The extensometer is held in place by the clamps 25 and 26 having adjusting screws The extensometer structure supported bythe clamps is' mounted upon ahousing 3ll madeup of cheek plates 3| and 32 united by spacers 33. Mounted, upon and suitably integral with the cheek plates at a point adjacent to and in line with the gauge pin 23, are located knife edges 34 directed toward the object 29 under test at'the gauges mark 2|. Cooperating with the knife edges 34 is a preferably circular bearing shaft 35 having knife edge slots 36 on one side near each end of the bearing shaft. The bearing shaft passes through a hole 31 in a lever block 38 and protrudes ateach end from the lever block for The engagement of the knife edge slots 36 with knife edges 34. The fit between the bearing shaft and the lever block is conveniently made a light drive fit so that in case of breakage of the bearing shaft, which may occur frequently, the broken bearing shaft can readily be driven out and the new bearingshaft-readily drivenin;

The lever block is preferably integral with and in many cases supports the gauge pin 23.

Lever block on the opposite end from the gauge-,4

.pin 23 is slotted preferably clear across at 49 transverse to the bearing shaft and the'slotis preferably extended at 4| acrossa portion of the section of the bearing shaft. This-feature-weakens the bearing shaft and may predispose it to breakage as in the Metzger form, but the bearing shaft is in any case very cheaply made and readily replaceable in the new form. Extending across 1 the slot and supported on the walls of the lever block- I provide a spring abutment 42, suitably inthe: formof a pin, which engages a hookend 43; of a .leaf spring 4 4 suitably mountedby a spring clamp 45 in one of the spacers 33. Suit- ;ably surrounding the bearing :block, except for the opening 46' through which ,the spring enters, -I provide-a lever extension 41, extending in a direction opposite from the'gauge pin 23. The

lever-extension may desirably be a sheet metal stamping; The lever extension has openings at -48 on each side to pass the bearing shaft, and

inassembly is placed onthe lever block before the bearing shaft is inserted. The lever extension is also held inzplace' onthe lever block by 'a's crew 5B in a screw hole-5l of the block.

utt r/he opposite end of thelever extension t! engagement is made with the operating plunger 52 ofa dial micrometer 53 mounted on a bracket 54.

j In operation the lever will beassembled by first placing the lever block in the lever extrensidn and is l mited thereto by the screw 50. The bearing pin will then be driven 'thIOHgh'l'lGIGS in the lever extension and the lever block. The lever the spring against the spring abutment and e am i g the spring clamp.

'In case of' breakage of the bearing shaft this the extensoineter, driving the bearing shaft out of 'tne lever extension and lever block and insert- -in'g a new bearing block. Ins-case "the gauge pin -23 'sh'ows Wear or-is broken, this is readily repiaced by removing the lever, taking out the wearing shaft and inscr'tingthe new bearing block through removal of the screw 50. A

It will be evident by the present invention that it is possible to simplify and 'cheapen structure o'f th entire bearing, and particularly of the lever extension.

In View of my invention and disclosurevariawens-and moaificatitns to nieet'individual whim for part ul'ar need will doubtless become "evident t'o -other's--'skilled in the art, to plotain'alror part p'f the be'neiit s of invention without copying e strujcture shown, and. I, therefore, "claim all insofar 'a s' they .fall within "the reasonable spirit and scope of .my claims.

;II avin'g thus de'scribedmy invention, what I 'ijlaiin new and desire to secure by Letters 'Pate'rit'is:

rinse extensometer, cheekplates united tos p aced relation,-.cooperating knife edges on the cheek plates, a bearing shaft having knife is thenready for assembly, bringing the knife "edge slots against the kniie edges rand 'inserting is readily replaced by taking the lever out of the lever block and extending from the opposite end of the lever block from the gauge pin.

2; In an-extensometer, cheek plates united together in spacedre-lation, cooperating knife edges on-the cheek plates, a circular bearing shaft having knife edge' slots extending across the knife edges .with the knife edges in the slots, a lever "block between the knife edges having a transverse opening through which the bearing shaft passes, rigid with respect to the bearing shaft, a gauge pin integral with the lever block and transverse to the bearing.shaft, wallsforming aspring slot transverse of the bearing shaft on the opposite'side of the lever block from the gauge pin, a spring abutmenti-n the ispring slot,. aspring acting on the spring abutment from the cheek plates, and a' lever extension removably secured to the lever block and extending from the'opposite end of; the lever block from the gatugev pin.

3. In an extensometer, cheek platesrunited to- }gether in spaced relation, cooperating knife-edges on the cheek plates, a circular bearing-shaft having knife edge slots; exten'dingzacross the knife edges with the-knife'edges in the slots, a:-lever block between theknife edges having a transverse opening through which the bearing shaft passes, rigid with respect to the bearing shaft, a gauge pin integral with the lever vblack and transverse to the bearing shaft, walls forming a spring slot transverse of the bearing shaft on the opposite side of the lever block from the :gauge pin, the spring slot extending across the bearing shaft, a springabutment in the spring slotya spring acting on the spring abutment, from the cheek plates, and a lever extension removablylse- --curedto the lever block and extending from the "opposite end of the lever block from the gauge pin.

4. An extenso'meter lever comprising .a bearing shaft having longitudinal knife edge slots ,on one side near its ends, a IIGVEIiblOCk having .a transverse opening in which the central portion of the bearing shaft is held, a gauge pin extending transversely of the bearing shaft and mounted on the lever "block, and a lever extension surrounding the lever block, having openingspassing "the ends of the bearing shaft removably secured :to the lever block and extending oppositely from the gauge pin.

5. An :extensometer flever comprising a bearing shaft having longitudinal knife edge slots on oile-"side nearfits ends, a lever block ,having a transverse opening in which thecentral portipn of. the bearing shaft is held, -a gauge pin extending transversely of the-bearing-fshaft and mounted on the lever block, wallsf'formifiga slotacross the opposite face or the lever block from-the gauge pin'an'd-a'cross the bearing shaft, aspring abutment in the slot, and a lever extension surrounding :the lever bicck having openlings passing the ends of the bearing shaft, removably secured -.to the le've'r'blockand extendingioppositely from the gauge pin..

. FRANZ C. :MOSTERTZ. No -referenue'swcited. r V 

